How Do I Turn a Mechanical Signal Into an Action Potential?

The brain is picking up information from the outside world about the world, and this is going to take information to our central nervous system to make sense of it. The question is how do I turn a mechanical signal into something that throws positive sodium and calcium into a neuron? So you'd have mechanical receptors. And then they will get to the point where they will put enough sodium in that it comes up to threshold. And then that will elicit an action potential.